1. Field of the Invention
The present invention relates to an optical disk drive or an optical disk recording/reproducing system. More particularly, the present invention relates to an apparatus for and a method of detecting a wobble signal, e.g., a harmonic modulated wobble (HMW) signal, in accordance with a time shift in an optical disk drive, e.g., a blue-ray disk (BD) drive.
2. Description of the Related Art
Blue-ray disks (BDs), which are used in general digital broadcasting, can store a significantly large amount of data compared with laser optical disks, for example, compact disks (CDs) or digital versatile disks (DVDs). In particular, an optical disk drive should be able to detect HMWs from a BD, land pre-pits (LPPs) from a DVD-read only memory (DVD-ROM), addresses in pre-grooves (ADIP) from a DVD recordable and rewritable (DVD+R/RW), and complementary allocated pit addressing (CAPA) from a DVD random access memory (DVD-RAM) to obtain an address, i.e., track position information, required to record information onto a blank disk.
FIG. 1 illustrates wobble information recorded to a general BD. Referring to FIG. 1, a track of the BD may be divided into a monotone unit, a reference unit, a synchronization unit including sync—0 through sync—3 units, and a data unit including a data—0 unit and a data—1 unit according to a minimum shift keying (MSK)-cosine variant and a HMW method. Each unit may include a MSK mark, a monotone wobble, a sawtooth wobble representing “0”, and a sawtooth wobble representing “1”. Each wobble in the BD may have a period of 69 T, where T is a channel clock signal.
FIG. 2 illustrates a block diagram of a general BD drive 200. Referring to FIG. 2, the BD drive 200 may include a spindle motor 210, a sled motor 220, a pickup apparatus 230, a servo control unit 240, a recording and reproducing unit 250, a wobble signal detection unit 260, and a system controller 270.
A BD may be provided on a rotational shaft of the spindle motor 210 and rotates. The pickup apparatus 230 may read data from the BD or write encoded data to the BD under the control of the servo control unit 240. The servo control unit 240 may drive a tracking actuator (not shown) and a focusing actuator (not shown) which may be included in the pickup actuator 230. The system controller 270 may control the spindle motor 210, the sled motor 220 and the servo control unit 240 to achieve tracking control.
Audio or video data may be recorded in numerous forms, e.g., pits or spiral tracks of the BD having a structure as shown in FIG. 1. During reproduction, an optical device included in the pickup apparatus 230 may follow the spiral tracks and may produce a radio frequency (RF) signal RFO from data recorded on the BD. During recording, the pickup apparatus 230 may receive encoded data from the recording and reproducing unit 250, process the encoded data and record the processed data on the tracks of the BD, e.g., as pits. The system controller 270 may transmit data decoded by the recording and reproducing unit 250 to a postprocessor or data received from the postprocessor to the recording and reproducing unit 250.
The wobble signal detection unit 260 may process the RF signal RFO produced by the pickup apparatus 230 to generate a wobble signal WOBB, which is unique for each disk. When data is recorded to a blank disk, the wobble signal WOBB is used as accurate address information about a track currently being followed. The wobble signal WOBB may be provided to the system controller 270 and may serve as a base signal for producing a timing clock signal used to control the spindle motor 210, the sled motor 220 and the servo control unit 240. The wobble signal WOBB may also be used in executing ADIP.
A wobble detected from the BD may have the shape shown in FIG. 3. Referring to FIG. 3, a monotone wobble signal 31 may have a “cos {2π(fw)t}” waveform. A sawtooth wobble 32 representing “1” may temporally lead the monotone wobble signal 31 and has a “cos {2π(fw)t}+a*sin {2π(2fw)t}” waveform. A sawtooth wobble 33 representing “0” may temporally lag the monotone wobble signal 31 and has a “cos {2π(fw)t}−a*sin {2π(2fw)t}” waveform. Here, fw is a wobble frequency and “a” may be a constant smaller than 0.5.
Conventionally, to obtain “0” or “1” from the sawtooth wobbles 32 and 33, a difference between the amplitudes of the sawtooth wobbles 32 and 33, and the amplitude of the monotone wobble signal 31 has been used. To achieve this, the RF signal RFO produced by the pickup apparatus 230 may be sampled periodically, the sampled RF signal RFO may be converted into a digital signal, and a code for a sawtooth wobble may be determined according to a current sampled value of the digital signal. However, the wobble frequency fw has 956.52 kHz at a 1×speed. The above-described conventional determination requires a high-speed analog-to-digital converter (ADC) and cannot resolve data for speeds over a range from a low speed to a high speed.